1. Field of the Invention
The present invention relates to technology for calibrating ink ejection amount for a printer that forms ink dots on a printing medium while scanning a print head unit in the main scan direction.
2. Description of the Related Art
Inkjet printers print images by ejecting ink from nozzles provided on a print head. The same as with other types of printers, for inkjet printers as well, there is always a pursuit of improvements in quality and improvements in printing speed. In recent years, the inkjet printer image quality has improved at about the same level as silver salt photographs, so improvement of the printing speed is a bigger problem.
To improve printing speed, the easiest measure is to increase the number of nozzles per color. As a method of increasing the nozzle count, it is possible to use a method that uses a plurality of print heads, for example.
However, it is normal for the ink ejection amount from a print head nozzle to contain manufacturing discrepancies. JP5-162338A and JP10-795A each describes a method of calibrating ink ejection amount that takes this kind of error into consideration.
Calibration of ink ejection amount is performed according to an ink ejection amount error. However, sufficient mechanisms were not implemented for determining an ink ejection amount error with respect to each print head. In particular, after assembling printers which comprise a plurality of print heads, there were cases when it was not easy to determine an ink ejection amount error for each of the print heads of that printer. Also, this kind of problem is not limited to printers that use a plurality of printing heads, but generally is a problem that is common to printers that comprise a printing head unit that has a plurality of nozzle arrays for ejecting same ink (called a “same ink nozzle array”).